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The Latest Word on Vitamin D
The Latest Word on Vitamin D
In the past few years, many claims have been made about vitamin D. More recently, there has been some observational evidence that vitamin D supplementation lowers the risk of breast and colorectal cancer. Although various health agencies have made guidelines on vitamin D, the recommended amounts vary. Should everyone take supplements? If so, how much? Understanding current recommendations and how this vitamin works in your body can help you to decide for yourself.
What is vitamin D?
Vitamin D has been called the ‘sunshine vitamin.’ Vitamin D helps the body use calcium and phosphorus to build, grow, and repair bones and teeth, improves muscle strength and immune function, and reduces inflammation.
Vitamin D comes in three ways – through sun, diet, or supplementation. Most people get vitamin D through sunlight exposure. Vitamin D may be obtained through diet.However, few foods naturally contain vitamin D. It is found in fatty fish, including sardines, tuna and salmon, and egg yolks. In Canada, vitamin D is added to milk. Supplements are another source.
In children, a lack of vitamin D can lead to rickets. This can deform the skeleton. Infants fed only breast milk (without supplemental vitamin D) may develop rickets. In adults, too little vitamin D is linked to osteoporosis (fragile bones). New research suggests vitamin D may protect against high blood pressure and cancer. It may also avert several autoimmune diseases in which the body attacks its own cells.
Too much vitamin D may cause calcium to be deposited in the body, especially in the kidneys, heart, lungs and blood vessels.
Food sources of Vitamin D |
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| Cod liver oil Mackerel, cooked Salmon, canned Sardines, canned Milk fluid Rice beverage, fortified Soy beverage, fortified Egg, whole Butter Margarine |
1 tsp / 5 mL 3½ oz / 100 g 3½ oz / 100 g 3½ oz / 100 g 1 c / 250 mL 1 c / 250 mL 1 c / 250 mL 1 large 1 tsp / 5 mL 1 tsp / 5 mL |
450 IU 345 IU 360 IU 270 IU 100 IU 100 IU 100 IU 25 IU 2.6 IU 20 IU |
What makes me likely to need more vitamin D?
- Aging – as we age, our skin becomes less able to make vitamin D from sun exposure.
- Darker skin – darker pigment acts as a natural sunscreen, making it harder for the body to create vitamin D.
- Lack of sun exposure – someone who does not go outside often, or wears clothing that covers most of the skin, may not get enough exposure to sunlight.
Is there new evidence about vitamin D?
Most of the hype around vitamin D this past year has focused primarily on cancer. Observational studies found that vitamin D supplementation lowered breast cancer and colorectal cancer. A large number of scientific studies have investigated a possible role for vitamin D in cancer prevention.
Many studies show the positive effects of vitamin D. However, many of these studies are observational or based on epidemiology, the study of factors affecting the health and wellness of populations. They are not controlled studies involving a placebo, which is the highest standard for a study. There is not much data on an ideal level of vitamin D for humans. Epidemiology studies found people with diseases like high blood pressure, diabetes and heart failure also had low vitamin D levels.
In 2007, an analysis of several quality studies showed that those over age 50 taking vitamin D supplements have a lower overall risk of early death. Evidence supports its use in several disorders affecting the density and strength of bones, in psoriasis, and for muscle weakness and pain.
How do I know if I lack vitamin D?
Unfortunately, there is little evidence to guide clinicians on when to screen for vitamin D deficiency, or how to use it effectively. However, research on the relationship between vitamin D and health suggests increasing the recommended daily amount.
Should I take vitamin D supplements? How much do I need?
Terms & abbreviations for recommended amounts of Vitamin D |
|
| Daily Reference Intakes | DRI |
| Estimated Average Requirement | EAR |
| Recommended Dietary Allowance | RDA |
| Adequate Intake | AI |
| Tolerable Upper Level of Intake | UL |
A Statistics Canada study published in March 2010 indicated that 1.1 million Canadians or about four per cent of the population are vitamin D deficient, or have levels low enough to cause rickets in children and osteoporosis in adults.
If you eat a healthy diet that includes milk and milk alternatives (such as fortified soy or rice beverages), are regularly outside in the sun, have light skin, and are under age 50, you may not need supplements. However, blood tests show that many people lack vitamin D, particularly during the winter months. Various Canadian agencies have made recommendations about the amount of vitamin D one should take.
Health Canada is in the process of changing and updating recommendations, as the last updates were done in 1997. A review board of Canadian and American scientists set these nutrient reference values for vitamin D (see sidebar). Many researchers view Canada’s standards as outdated, as these guidelines were based mainly on low levels of vitamin D needed to prevent childhood rickets.
Adequate Intake (AI) values for Vitamin D |
|
| 0 - 1 year | 200 IU per day |
| 2 to 50 years | 200 IU per day |
| 51 to 70 years | 400 IU per day |
| Older than 70 years | 600 IU per day |
| The Tolerable Upper Level of Intake (UL) for those over age one is 2000 IU/day. For pregnant women the UL can range between 1000 IU/day and 4000 IU/day. | |
Canada’s Food Guide recommends men and women over age 50 take a 400 IU vitamin D supplement daily. Osteoporosis Canada recommends 400 IU per day for those aged 19 to 50. It recommends 800 IU per day for people over 50. Supplements may be necessary, as few foods contain vitamin D naturally.
The Canadian Cancer Society (CCS) recommends 1,000 IU of vitamin D every day. During spring and summer, many can get this amount from normal daily exposure to the sun. However, a supplement may be necessary in fall and winter. The CCS also suggests that those who are older, have dark skin or little sun exposure consider taking 1000 IU of vitamin D daily year-round.
Health Canada recommends that all breastfed babies receive 400 IU of vitamin D daily. A daily supplement of 800 IU is suggested for breastfed babies living in Canada’s northern communities, or above the 60th parallel. Babies should receive a supplement until they are eating foods that provide them with the vitamin D they need.
What is the bottom line?
It is likely that most people living in Canada lack vitamin D. Adults living in Canada should consider increasing their intake during fall and winter. Because of our northern climate, we must get vitamin D from food sources and supplements to meet our vitamin D requirements.
Most multivitamins found over-the-counter contain 400 IU of vitamin D. It may be bought by itself as a 400 or 1000 IU amount, or combined with calcium and other minerals. It is important to supplement your diet with 1000 IU a day of vitamin D. If you take a supplement of 1000 IU, there is no need to be concerned if your intake is slightly above that, as a number of experts feel that the 2000 IU upper limit is too low.
More evidence is needed before blood screening for low levels of vitamin D becomes routine. Many researchers suggest current guidelines for vitamin D may be too low. New research will increase understanding about the best doses of vitamin D.
If you think you may not be getting enough vitamin D, talk to your doctor, pharmacist or registered dietitian. Eat a healthy, well balanced diet that follows Canada’s Food Guide.
FAMILY HEALTH is written with the assistance of |
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FAMILY HEALTH is written with the assistance of |
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